The invention is based on a pressure sensor module for measuring a differential pressure.
In sophisticated engine control systems, the fuel pressure is regulated in order to reduce fuel heating and to lessen the emissions of fuels. With the aid of a fuel pressure sensor, the difference between the fuel pressure and the intake tube pressure is measured. Currently, silicon-based micromechanical sensors are used as economical fuel pressure sensors. In them, one side of a diaphragm, remote from a circuit, is subjected to fuel, and one side of the diaphragm, toward the circuit, is connected to the intake tube. If the sensor diaphragm breaks because of mistakes in production or handling, the fuel will be pumped through the burst diaphragm directly into the intake tube, where it can cause destruction of the engine from fuel impact.
Differential pressure sensors are known that on a compression side additionally have a metal diaphragm, upon which the pressure is exerted and which transmits this pressure to the sensor diaphragm via a silicone oil. If the diaphragm of the sensor breaks from an overload, the metal diaphragm presses against a support face that is provided and absorbs the pressure, so that the medium on the compression side cannot get into the sensor housing and/or into the region of the other compression side. Only a slight quantity of the silicone oil that is present reaches the inside of the intake tube.
However, because of their complicated structure for the metal diaphragm and the embodiment of the hermetically sealed volume for the silicone oil, these sensors are expensive. This is due to the material and process costs for the connection technology, the oil filling, and calibration after the oil filling has been done. To meet the required precision, a minimum size of the metal diaphragm and thus also a corresponding structural size are required, which is a hindrance to miniaturization.
From British Patent GB 2264070 A1, a device is known that has a differential pressure sensor and a valve that can close a lead line to the differential pressure sensor. This can be done only via an electronic controller.
In keeping with these objects, a pressure sensor module in accordance with the present invention has a sensor chip for measuring a differential pressure and a module housing having at least two lead lines that are disconnected from one another by the sensor chip, and different pressures are present in the lines at least intermittently wherein in accordance with the present Invention in at least one lead line a valve is disposed that closes these lead lines when the sensor chip no longer disconnects the lead lines from one another.
The pressure sensor module of the invention has the advantage over the prior art that in a simple way, a transfer of a medium from one lead line to another lead line is prevented, and this is accomplished independently of the pressure and independently of the flow of the medium.
One advantageous feature of a valve is attained by providing that a lift body is disposed between two constrictions of a lead line and closes this lead line by pressing against one constriction, if a sensor chip no longer disconnects the lead lines from one another.
A constriction can advantageously be formed by a perforated grid.
As the lift body, a ball with a smaller cross section than the lead line is advantageously used.
An advantageous embodiment of the invention is recited in claim 6, in which the pressure sensor module is connected to an intake tube of an internal combustion engine and to a fuel line.
It is advantageous if the pressure sensor module is installed vertically, because as a result the lift body does not close the lead line in an unwanted manner.
It is advantageous if the lift body has a lesser density than the fuel, since the lift body, because of its buoyancy in the fuel, presses against the second constriction and thereby closes the line, so that fuel cannot get into the intake tube.
It is advantageous if the constriction or the lift body additionally has sealing elements, which facilitate sealing.
For guiding the lift body, the lead line advantageously has guide rails, which assure that the lift body will always optimally come to rest against the constriction, and that in normal operation, there is sufficient space available for an exchange of media upon changes in the intake tube pressure.